The Role of Residential Segregation in Treatment and Outcomes of Ductal Carcinoma in Situ of the Breast

Background: It remains unclear if residential segregation impacts on clinical treatment and outcomes for ductal carcinoma in situ (DCIS), a nonobligate precursor to invasive breast cancer (IBC). Methods: This population-based retrospective cohort study included adult non-Hispanic White (NHW) and Black (NHB) women diagnosed with unilateral DCIS between January 1990 and December 2015, followed through December 2016, and identified from the Surveillance, Epidemiology, and End Results dataset. County-level racialized economic segregation was measured using the Index of Concentration at the Extremes. Multilevel logistic regression and Cox proportional hazards regression accounting for county-level clustering were used to estimate the odds ratios (ORs) of local treatment, and hazard ratios (HRs) of subsequent IBC and mortality. Results: Of 103,898 cases, mean age was 59.5 years, 12.5% were NHB, 87.5% were NHW, 97.5% underwent surgery, 64.5% received radiotherapy following breast-conserving surgery, 7.1% developed IBC, and 18.6% died from all causes. Among women living in the least vs most privileged counties, we observed higher odds of receiving mastectomy (vs breast-conserving surgery) (OR=1.51, 95% CI 1.35-1.69; Ptrend<0.001) and radiation therapy following breast-conserving surgery (OR=1.27, 95% CI 1.07-1.51; Ptrend<0.01); the risk was higher in subsequent ipsilateral IBC (HR=1.16, 95% CI 1.02-1.32; Ptrend=0.04), not in breast cancer-specific mortality (HR=1.04, 95% CI 0.88-1.23; Ptrend=0.56). Conclusions: The results provide evidence for disparities in clinical treatment for DCIS and prognostic outcomes among women in racially and economically segregated counties. Impact: Our findings may inform geographically targeted multilevel interventions to reduce breast cancer burden and improve breast cancer care and equity.